Mad Max style "funny front" motorcycle I built at local hacker space


#1

Had a post about this before, but was a LONG time ago so now closed. Much progress since then - the bike is actually finished and (roughly) ride-able. In fact, it is currently at a mechanics shop getting carb work done to resolve … well, the fact it has 37 year old carbs and was pulled apart and rebuilt, basically. It actually starts pretty nicely when cold, but after a minute or so either dies or revs up to idle at 5,000 rpm. I was able to limp it around the block in that condition, but it obviously needed work and while I can shape metal, even moving bits, I’m not a mechanic.

I have an imgur album with build / engineering info that might answer some common questions re design and safety - http://imgur.com/a/VR3WH


#2

That tight front end kinda freaks me out a bit but otherwise really cool project!


#3

Tight as in close to the wheel, or steep rake? It is both.

The arm lengths are adjustable, so I played around a bit (with the bike’s frame jacked up on a stand and the spring perch loose on the shock) seeing how short I could get the wheelbase without anything clashing during suspension travel.

Adjustable arm length means adjustable rake; the trail is also separately adjustable vie the connection to the top of the fork. I was shooting for 20 degrees or less, which obviously is very steep, but trail would still be the conventional 3-4 inches. The thinking there comes from the info in this article - https://tonyfoale.com/Articles/RakeEx/RakeEx.htm

I ended up a bit over 21 degrees, which gives me dimensions much like a Buell XB12S Lightning scaled up 15% (bigger wheels, longer wheelbase). Its got a steering damper mounted directly from the fork to suspension arm just in case the setup does want to cause shakes at speed.


#4

Is it comfortable to ride?


#5

It’s build to my proportions (I’m 6’3" with a 33" inseam). I’ve built up a few bicycles with similar ergonomics, and they were quite comfortable for me. Like any bike without a fairing, long rides on the highway might get annoying. Haven’t had it up to speed yet, just sat on it in the shop and stumbled it around the neighborhood once.


#6

My Africa Twin is slowly turning to look like something from a Mad Max movie.
It’s not a project as such; I just crash it every now and then and patch it up.
Black duct tape looks a bit like those carbon fibre accesories and decals you can buy.


#7

That explains why the proportions look a bit odd, you’re even bigger than me.

One of the great things about DIY is having stuff fit the end user.


#8

Well, the proportions are a bit odd. Because mine are. The seat is only up 2 inches, but the bars are down 6 and out a whopping 10 because of my freakish torso & arm length. That still leaves me more upright than a normal rider would be on a sport bike.

But yeah, coming from the bicycle world, where even cheap bikes come in multiple sizes, I’m surprised how little attention motorcycle manufacturers pay to rider fit. At best you maybe get an adjustable seat.


#9

… and having stuff fit the user’s ‘end’.

:slight_smile:


#10

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